Natural Image Quality Evaluator (NIQE): NIQE [1]} is a completely blind image quality assessment method. Without the requirement of knowledge about anticipated distortions in the form of training examples and corresponding human opinion scores, NIQE only makes use of measurable deviations from statistical regularities observed in natural images. It extracts a set of local (quality-aware) features from images based on a natural scene statistic (NSS) model, then fits the feature vectors to a multivariate Gaussian (MVG) model. The quality of a test image is then predicted by the distance between its MVG model and the MVG model learned from a natural image:
\(\begin{small}D(\nu _1,\nu _2,\Sigma _1,\Sigma _2)=\sqrt{((\nu _1-\nu _2)^T(\frac{\Sigma _1+\Sigma _2}{2})^{-1}(\nu _1-\nu _2))},\end{small}\) 
